#include <iostream>
#include <string>
using namespace std;
// write your code here......
void inverse(string &s)
{
    string r;
    for (int i = 0; i < s.length(); i++)
        r[i] = s[s.length() - i - 1];
    s = r;
}
int main()
{
    string s;
    getline(cin, s);
    // write your code here......
    inverse(s);
    cout << s;
    return 0;
}

为什么这样不行呀